Characterization and removal mechanism of a novel enrofloxacin-degrading microorganism, Microbacterium proteolyticum GJEE142 capable of simultaneous removal of enrofloxacin, nitrogen and phosphorus

In the study, a novel ENR-degrading microorganism, Microbacterium proteolyticum GJEE142 was isolated from aquaculture wastewater for the first time. The ENR removal of strain GJEE142 was reliant upon the provision of limited additional carbon source, and was adaptative to low temperature (13 ℃) and high salinity (50‰). The ENR removal process, to which intracellular enzymes made more contributions, was implemented in three proposed pathways. During the removal process, oxidative stress response of strain GJEE142 was activated and the bacterial toxicity of ENR was decreased. Strain GJEE142 could also achieve the synchronous removal of ammonium, nitrite, nitrate and phosphorus with the nitrogen removal pathways of nitrate → nitrite → ammonium → glutamine → glutamate → glutamate metabolism and nitrate → nitrite → gaseous nitrogen. The phosphorus removal was implemented under complete aerobic conditions with the assistance of polyphosphate kinase and exopolyphosphatase. Genomic analysis provided corresponding genetic insights for deciphering removal mechanisms of ENR, nitrogen and phosphorus. ENR, nitrogen and phosphorus in both actual aquaculture wastewater and domestic wastewater could be desirably removed. Desirable adaptation, excellent performance and wide distribution will make strain GJEE142 the hopeful strain in wastewater treatment.

Isolation and Aflatoxin B1-Degradation Characteristics of a Microbacterium proteolyticum B204 Strain from Bovine Faeces

Aflatoxin B₁ (AFB₁) is one of the most harmful mycotoxins, raising serious global health and economic problems. Searching for biological approaches for effective and safe AFB₁ degradation is imminent. In our study, Microbacterium proteolyticum B204 isolated from bovine faeces degraded 77% of AFB₁ after 24 h, becoming the first reported bacteria from the Microbacterium family to possess AFB₁ degradation characteristics. Temperature variation showed little effect on its degradation ratio, demonstrating high thermostability of 75% and 79% after boiling and sterilization, respectively. We suppose that the components playing a key role during this process were proteins, considering the decreased degradation rate caused by Proteinase K. Cell viability detection on HepG2 cells indicated that the degradation products were much less toxic than pure AFB₁. Furthermore, B204 cell-free culture supernatant also degraded AFB₁-contaminated food, such as peanuts, corn and cheese. These results suggested that this strain with AFB₁ degradation properties could be a prospective candidate for application in the food and feed industries.